It is common that during data transmission amplitude or phase modulation of the transmitted information is used by using a carrier and a subcarrier signal. The standard for contactless communication ISO 14443 characterizes the conditions of the A or B modulation with carrier signal having the 13.56 MHz frequency. The data transmitted are modulated into the subcarrier frequency in the transmitter and the subcarrier frequency is combined with the basic, carrier signal. The result will be a frequency superposition with transmitted data, that are detected in the receiver by separation of the carrier signal from the received spectrum. For short-distance data transmission, a transformer connection between the antenna systems of the receiver and the transmitter is used. When using a transformer connection, the frequency signal does not have to be actively transmitted; it is sufficient if the induction circuit of the transponder antenna is short-circuited on a needed frequency. These changes on the transponder's side can be measured on the receiver's antenna output. This configuration is common in contactless communication between cards and the readers of the cards.
During transmission from the shielded or more remote transponder, the transformer connection is weak, with the coefficient being k=0.2-0.001, which considerably deteriorates the transmission characteristics of the communication channel. Nevertheless, the transponder's antenna system must be capable of transmitting the frequency spectrum which includes the carrier and subcarrier frequency. This situation is shown on the FIG. 1. In specific conditions, e.g. in case the transponder is shielded or interfered with, it is necessary to improve the transmission characteristics of the system, to lower noise and to improve the reception of the signal being received, all without requiring increase in the radiated power.
The existing technical solution enables a reliable data transmission from the contactless cards, e.g. from the payment cards in case the card is within the operating volume of the reader and in case the card is not shielded or interfered with. Along with the development of new functions of the mobile communication devices, there is a tendency to place the payment card into the mobile communication device, which deteriorates the transmission characteristics of the pair transponder-reader; the deterioration is up to the point when transmission failure takes place in common non-laboratory conditions. Also, in case of other transmission systems, it is required to reduce noise and improve the possibilities of antenna system's tuning.
The technical solutions as in patent files WO 2004/107595A1, EP 2101278A2, U.S. Pat. No. 5,955,950, WO 2005/104022A1, EP 1403963 B1, CN 201075228 describe connections enabling better detection of a received signal or possibilities of antenna tuning; however these always require changes on the side of the receiver and it is not possible to expect dramatic improvement of the transmission in weak transformer connections. Such a technical solution that will improve transmission characteristics of the system and that would not require any changes in the hardware and software of already used readers is required.
The technical problem can be in general solved even by a new, purpose-designed dimensation of the transmitter-receiver pair. However, in case when in business practice there are receivers e.g. in the form of the POS terminal readers that are massively used, it is practically impossible to put new readers through widely and quickly. Above all, this problem arises during introduction of new transmission channels based on contactless communication elements located on the removable memory card in the mobile phone according to Logomotion's other solutions. The common solution that is on hand to a average technician is not usable for this reason.